Reducing Management and Research Disturbance 19

351 Reducing 19 Management and Research Disturbance

ROBERT N. ROSENFIELD effects of various toxic chemicals have produced a rich Department of Biology, University of Wisconsin literature (Parker 1976, White et al. 1989, Goldstein et Stevens Point, WI 54481 U.S.A. al. 1996, Mineau et al. 1999, Klute et al. 2003, Ratcliffe 2003). Other threats to raptor populations stem from the JAMES W. GRIER loss and degradation of habitat due to logging, agricul- Department of Biological Sciences, North Dakota State University ture, industrial pollution, climate change, recreational Fargo, ND 58105 U.S.A. activities, weapons-testing noise, and even still, direct persecution through shooting, trapping, and poisoning RICHARD W. FYFE (Bildstein et al. 1993, White 1994, Fuller 1996, Kirk Box 3263, Fort Saskatchewan, Alberta, T8L 2T2 Canada and Hyslop 1998, Brown et al. 1999, Fletcher et al. 1999, Wood 1999, Noon and Franklin 2002, Klute et al. 2003, Newbrey et al. 2005). Impacts of researcher disturbance on breeding raptors also have been documented, including nesting failures after climbs to nests INTRODUCTION (Boeker and Ray 1971, Luttich et al. 1971), lowered nesting success (Wiley 1975, Buehler 2000), and dis- Researchers may disturb raptors in several ways during placement of birds from home ranges (Andersen et al. breeding or other seasons, and in so doing skew the 1986, 1990). results of their fieldwork. For example, disturbance may That said, many species of raptors worldwide be a problem in achieving unbiased estimates of repro- recently have found ways to co-exist and breed success- ductive success and other behavior. It is thus desirable fully in human-altered and occupied environments, to understand and minimize the effects of disturbance often nesting on man-made structures such as power- on research work and on the birds themselves. Because line poles, buildings, smoke-stacks and bridges (e.g., raptor conservation has received considerable attention, Bird et al. 1996). Although raptors as a group often are we have much information on the actual or potentially described as being sensitive to human disturbance, deleterious effects that researchers and managers have especially when nesting (Newton 1979, Snyder and had or may inflict on raptors. In this chapter we discuss Snyder 1991, Roberson et al. 2002), recent studies some of the problems associated with research and report numerous populations of “forest” raptors nesting management disturbance to raptors and offer possible successfully in human-dominated landscapes. For solutions. example, 70 breeding territories of Northern Goshawks Destructive effects of human activity on raptors are (Accipiter gentilis) were found within Berlin, Germany varied and rather well documented in both non-techni- in 1999 (Krone et al. 2005). Cities, in fact, now harbor cal and technical publications. The sub-lethal and lethal some of the highest nesting densities yet recorded for 352 REDUCING MANAGEMENT AND RESEARCH DISTURBANCE some woodland and forest species, including Mississip- White and Thurow 1985, Crocker-Bedford 1990). Also, pi Kite (Ictinia mississippiensis) (Parker 1996), Red- because raptors tend to nest at relatively low densities, tailed Hawk (Buteo jamaicensis) (Stout et al. 2006) and the effects of disturbance may be harder to detect Cooper’s Hawk (A. cooperii) (Rosenfield et al. 1995, because of difficulties in collecting large enough sam- Boal and Mannan 1999). ples of nests (Gotmark 1992; but see Riffel et al. 1996). Raptor scientists have documented behavioral and Researcher disturbance per se is not mentioned in some demographic differences between raptors nesting in reviews of management efforts for various raptor rural areas where disturbance is reduced and those nest- species of high conservation profile (Cade et al. 1988, ing in relatively high-disturbance settings including Reynolds et al. 1992, Klute et al. 2003, Andersen et al. urban areas where birds are more habituated to human 2005). However, one report (United States Fish and presence and are less wary and, sometimes, more Wildlife Service 1998) stated that observations of nests aggressive as well (Götmark 1992, Steidl and Anthony for short periods after the young hatch, or trapping of 1996, Bielefeldt et al. 1998, Aradis and Carpaneto 2001, adults for banding or attaching radio transmitters during W.E. Stout and A.C. Stewart, pers. comm.; see also nesting, did not cause nest desertion. The report con- Andersen et al. 1989). Northern Goshawks in Britain, cluded that disturbance usually is not a significant fac- central Europe, and Japan nest in close proximity to tor affecting the long-term survival of any North Amer- humans in rural landscapes where some populations are ican goshawk population. not especially prone to disturbance (Squires and Grier (1969) found no disturbance effects from a Kennedy 2005). The docile behavior and interactions large-scaled, three-year, controlled experimental study with humans, for instance, indicate low levels of direct of possible effects from climbing to Bald Eagle (Hali- human impact on the Spotted Owl (Strix occidentalis) aeetus leucocephalus) nests in northwestern Ontario, (Gutierrez et al. 1995). Canada. Similarly, Steenhof (1998) indicated that prop- There are several reviews of negative human erly designed field studies have no measurable effect on impacts on raptors (e.g., Stalmaster and Newman 1978, Prairie Falcon (Falco mexicanus) populations; and that Newton 1979, Keran 1981; see also various species during 24 years of research on this species in the Snake accounts on raptors in the Birds of North America series River Birds of Prey Natural Conservation Area in Idaho, [Poole 2004]). Much literature suggests that human dis- investigators caused egg or nestling losses at only 11 turbance is a problem during the nesting period, espe- (0.7%) of 1,555 nesting attempts (Steenhof 1998). cially during incubation (e.g., Fyfe and Olendorf 1976, Likewise, during hundreds of thousands of hours of Boal and Mannan 1994, Roberson et al. 2002). Manage- research on and monitoring of Spotted Owls, including ment attempts to lessen such impacts, including buffer more than 2,065 captures with no deaths, there was no zones around nests and timed restrictions on activities, clear evidence of significant impact by research activi- are described by Stalmaster and Newman (1978), Suter ty except for a negative effect on reproduction from and Jones (1981), Grier et al. (1983), Squires and backpack radio transmitters (Gutierrez et al. 1995, see Reynolds (1997), Erdman et al. (1998), Jacobs and below). In a review that compared the effects of inves- Jacobs (2002), and Watson (2004). Attempts to mini- tigator disturbance at nests, non-raptors seemed to be mize investigator disturbance are varied and include more vulnerable to disturbance effects than were raptors actions such as building tunnels to observation blinds (Gotmark 1992). Although sample sizes were small, one (Nelson 1970, Shugart et al. 1981), limiting the duration possible reason for the disparity may have been that of nest visits (Rosenfield and Bielefeldt 1993a, Squires raptor biologists made comparatively fewer visits to and Kennedy 2006), and using small, silent cameras nests or employed relatively benign forms of distur- installed near nests to reduce or eliminate the need for bance compared with methods used to study other birds repeated visits to nests by observers (Booms and Fuller (Gotmark 1992). 2003, Rogers et al. 2005, Smithers et al. 2005). Because the problems of general human distur- The effectiveness of minimizing disturbance asso- bance are so diverse (Riffel et al. 1996) and are dis- ciated with research and management activities with cussed in Chapter 20, we focus on the responsibilities nesting raptors is rarely known or reported (Gotmark and possible consequences of the actions of researchers 1992). This is because disturbance is difficult to meas- and managers. Most literature on disturbance deals with ure and, generally, is not directly quantified by raptor research on breeding raptors. Fyfe and Olendorff (1976) researchers (but see Grier 1969, Busch et al. 1978, reviewed and provided excellent suggestions for reme- REDUCING MANAGEMENT AND RESEARCH DISTURBANCE 353 dying a variety of research and management distur- Craighead 1956]), or a shift of activity within home bance problems among nesting raptors. Below we sum- ranges (Andersen et al. 1990). marize their suggestions and offer modifications of Raptor scientists should contact the proper agencies some of their suggestions in light of Gotmark (1992), as for procuring research permits and, when appropriate, well as attempt to coordinate some of our recommenda- seek approval of field procedures from an animal-care tions with those presented elsewhere in this book. entity. Within the U.S. and Canada, wild birds are given legal protection through The Migratory Bird Treaty Act and the Migratory Bird Conservation Act, respectively. PRELIMINARY CONSIDERATIONS Any research that involves disturbing, handling, collecting, or in any way manipulating wild birds requires It is imperative that researchers and managers consult written approval from the appropriate Federal, State, or the technical literature, as well as knowledgeable per- Provincial regulatory authorities in North America. sons during the design of their projects to learn of Details regarding permit applications and wildlife pro- potential disturbance problems that could arise from tection in North America are in Little (1993), and can be field activities, along with ways to minimize such dis- obtained directly from the U.S. Fish and Wildlife Ser- turbance. They should not rely solely on literature as vice regional offices or the Canadian Wildlife Service, disturbance effects may not always be mentioned in or Provincial wildlife authorities as appropriate. In papers (Gotmark 1992). addition, researchers and managers working with rap- Some disturbance problems may be species- or site- tors also may need approval for projects including field specific, or both. For example, White and Thurow work from their institution’s Animal Care and Use (1985) found that Ferruginous Hawks (B. regalis) in Committee. Utah were quite susceptible to disturbance at their nest. When possible, we urge researchers and managers to In some areas but not others, Swainson’s Hawks (B. seek training on the use of techniques by participating in swainsoni) may desert their nests if they are visited by workshops that provide, for example, field instruction by humans during incubation (Houston 1974, England et experienced biologists in the natural history of raptors al. 1997). Cooper’s Hawks in Wisconsin do not desert and their usual responsiveness to people, training on nests in trees climbed to count eggs (Rosenfield and how to find and monitor nests, and knowledge of ways Bielefeldt 1993a). However, Erdman et al. (1998) cau- to collect reproductive data by observing or climbing to tioned against flushing incubating, congeneric Northern raptor nests (e.g., Jacobs and Jacobs 2002). In Wiscon- Goshawks there; they do not climb to their nests to sin, Erdman et al. (1998) indicated that their workshops count eggs because they believe that such activity will and field training on the nesting biology of Northern cause the birds to desert their nest, although they did not Goshawks generated so much interest and cooperation document this effect. among U.S. Forest Service personnel that these employ- Within a population, most individuals exhibit varia- ees helped double the number of known goshawk terri- tion in behavioral responses to human presence (Grier tories in a national forest. Workshops often are 1969, Andersen et al. 1989, McGarigal et al. 1991, Got- announced in newsletters published by the Ornithologi- mark 1992), and some variation relates to the bird’s cal Societies of North America and by the Raptor activity at the time of approach. Snail Kites (Ros- Research Foundation. Appropriate government agency trhamus sociabilis), for example, are approachable on offices also are good sources of this information. their foraging grounds but tend to be very sensitive to An inadvertent and indirect cause of disturbance at human intrusion around nests (Snyder and Snyder nest sites involves public knowledge of the locations 1991). In response to human presence, breeding Bald and resulting attention. Problems can result if individu- Eagles were less likely to flush, and flushed at shorter als seek to deliberately harm or collect the birds, and distances to people than did nonbreeding adults (Steidl when well-intentioned individuals interfere by their and Anthony 1996). Successfully reducing disturbance presence at the site. Such disturbance from unautho- to raptors may call for close attention to their behavior rized falconers, photographers, birders, zoologists, and and a willingness to break off operations if signs of even wildlife managers is well known. As a result, sev- stress become evident, such as prolonged alarm calling, eral concerned wildlife groups have adopted resolutions extended absence of adults from a nest (during which recommending that such site information be kept confi- time predators may gain access to nests [Craighead and dential, but made available to the appropriate land man- 354 REDUCING MANAGEMENT AND RESEARCH DISTURBANCE agers. Problems result not only for the birds, but also for turbance. All four were deserted following extended persons working with them, including future access and visits of about 1 hour by field workers during the incu- spending money to guard and protect the sites. The bation stage (Rosenfield and Bielefeldt 1993a, R. obvious solution to this is maintaining the confidential- Rosenfield, unpubl. data). In all four instances, only ity of site-specific information, even in reports, gradu- females deserted; males tried unsuccessfully at all four ate theses, and scientific publications. In case of con- sites to incubate clutches for about 7–10 days following flicts with freedom of information laws or regulations, their mates’ desertion (R. Rosenfield, unpubl. data). site information may be placed under provisions of spe- Human activities near nests with young rarely cause cial protection or kept in the files of researchers or other nest abandonment, and then only because of severe dis- agencies not subject to public disclosure. Maps and site- turbance. For example, logging activities including cut- specific information also can be kept at widely dis- ting, loading, and skidding within 50–100 m of a persed locations, at various offices and in different files, goshawk nest can cause abandonment even when 20- with only statistical results stored in central, public day-old nestlings are present (J. Squires, unpubl. data). locations. Dispersed information would likely slow Intra-seasonal nest desertion due to researcher presence access by unauthorized persons, increase inability to is highly unlikely after young hatch, but Golden Eagle find all of the information, and facilitate detection of (Aquila chrysaetos) pairs whose young were banded in unauthorized use. Ellis (1982) refers to the treatment of three Rocky Mountain states were more likely to move information to ensure protection and privacy as “infor- to alternate nests or not breed the following year than mation management.” Information management is pairs whose young were not banded (Harmata 2002). extremely important and should be heeded by all per- Nesting Bald Eagles responded similarly in coastal sons working with birds of prey. Proper attention to British Columbia, Canada (D. Hancock, unpubl. data), information management not only will reduce distur- but no such effects have been found for Bald Eagles in bance, but also will greatly reduce or eliminate the need Ontario, where a study involving several thousand for eyrie wardens and other forms of site protection. climbs into nests revealed no difference in nesting success between nests that were climbed into and those that were not (Grier 1969). It also seems likely that little dis- BASIC RECOMMENDATIONS FOR turbance occurs to other adult raptors, including Eastern REDUCING DISTURBANCE AT NESTS Screech Owls (Megascops asio) and Barn Owls (Tyto alba), that are caught in nestboxes while incubating (Taylor 1991; K. Steenhof, per comm.). Nest Desertion Some species may be quite tolerant of various Nest desertion, which is serious, can be unpredictable. forms of researcher disturbance during the earlier pre- In general, the likelihood of desertion varies by nesting incubation and incubation periods. For example, using stage, among different species, among different individ- bait birds in traps set out before dawn, Rosenfield et al. uals within species, and probably gender. Nest desertion (1993b) captured 38 different adult Cooper’s Hawks due to researcher disturbance is poorly documented in (25 males, 13 females) at 41 nests that were under con- many studies. Nest desertion may be underestimated struction during the pre-incubation period in Wisconsin. because of the likelihood that abandoned nests may be Trapping at this time was expeditious because traps preyed upon or scavenged before they are detected were placed precisely where the hawks were expected (Gotmark 1992). It is generally believed, and some to appear at dawn. The hawks detected the human-con- studies show, that nest desertion due to disturbance is trolled movement of bait birds quickly and were usual- more likely to occur early, as opposed to late, in a sea- ly caught (or missed) within 0.5 hours. None of the son. For example, in an intensive 14-year study of nests were deserted and 98% of the 41 pairs laid eggs; Cooper’s Hawks in Wisconsin, involving multiple and whereas among 127 pairs they discovered at the pre- repeated sources of potential disturbance (e.g., attempts incubation stage and where trapping was not attempted, [often successful] to trap adults at all stages of nesting, 93% laid eggs (Rosenfield and Bielefeldt 1993b). climbs to nests to count eggs and band young), includ- No nest desertions occurred during 35 years of cap- ing an estimated cumulative total of more than 3,000 turing more than 400 adult Ospreys (Pandion haliaetus) visits over 3–4 months to 330 nests, only four (1.2%) in Michigan using a dome-shaped, noose “carpet” trap nests were known to have failed due to researcher dis- set over eggs or young (S. Postupalsky, pers. comm.). REDUCING MANAGEMENT AND RESEARCH DISTURBANCE 355

Adult Ospreys were attentive and were caught within rowhawk nests to allow for more accurate identification minutes during incubation, whereas trapping took 1 to 2 of prey (Newton 1978, Geer and Perrins 1981). Such hours during the nestling stage. Trapping of Ospreys close placement allowed the researchers to extend tongs always was done during rainless periods. Houston and through a hole in the blind to retrieve some of the song- Scott (1992) reported no “adverse effects” with the use bird prey that were leg-banded; prey were replaced with of noose carpets to trap adult Ospreys in Saskatchewan. the tongs after the bands were removed (Geer and Per- Slip-noose traps also have been used on nests during the rins 1981). Initially, the parent birds flew off when incubation period to trap adult Eurasian Sparrowhawks tongs were extended, but soon they became so accus- (A. nisus) in Scotland and Peregrine Falcons (F. peregri- tomed to the procedure that tugs-of-war developed over nus) in West Greenland, with no known desertions by prey items that the researchers tried to remove. Adult adults attributed to this disturbance (Newton 1986, W.G. Prairie Falcons also tolerate observation blinds within 2 Mattox, unpubl. data). Catching adult American m of their nests (Sitter 1983). Kestrels (F. sparverius) in boxes is a common technique Nesting adult raptors appear to habituate to blinds, that rarely results in disturbance unless it occurs during as well as to people entering and leaving them (e.g., egg-laying (K. Steenhof, pers. comm.). It also seems Geer and Perrins 1981, Steenhof 1998, but see Snyder that little disturbance occurs to other adult raptors (e.g., and Snyder 1991 for Snail Kites). Nest abandonment, Western Screech Owls [M. kennicottii] and Barn Owls) apparently, is rare, although researchers have generally caught in nest boxes when incubating (K. Steenhof, not detailed their procedures on blind placement and the pers. comm.). behavior of adults in response to human activity. Adult Cooper’s Hawks in Wisconsin also have been females returned to nests within 20 minutes of comple- caught during the incubation period using a mist net tion of blind set-up, and no desertions of nests occurred placed near plucking posts with an owl as a lure (Rosen- after blinds were installed in about 2 hours and within 5 field and Bielefeldt 1993a). The limbs and other perches m of nests when young were about 1 week old at each where males pluck and transfer prey to females are usu- of three Broad-winged Hawk and five Cooper’s Hawk ally about 50–100 m from the nest and typically out of nests in Wisconsin, and at four Peregrine Falcon nests in view of the nest. Males call immediately to their mates West Greenland (Rosenfield 1983, Bielefeldt et al. upon arrival at plucking posts, which also alerts the 1992, Rosenfield et al. 1995, R. Rosenfield, pers. obs). researcher hidden nearby to play a recording of a Coop- On the other hand, at a Gyrfalcon (F. rusticolus) nest on er’s Hawk alarm call to draw attention to the owl. Males, Ellesmere Island in 1973, the male, but not the female, the target of this technique, usually are caught within 15 abandoned a brood of four young when a wooden blind minutes after they detect the owl. If not, the researchers was relocated from hundreds of meters from the nest to immediately leave the nest area to minimize disturbance a spot approximately 12 m away (D. Muir and D. M. to the incubating female. This type of disturbance has Bird, pers. comm.). Blinds can be constructed during been used at 40 nests and resulted in captures of 35 short work periods (< 2 hours) over a series of days to males and, inadvertently, seven females (the other 33 reduce disturbance of parent raptors (Geer and Perrins females remained on their nests), with no nest desertions 1981, Boal and Mannan 1994). attributed to this technique (R. Rosenfield and J. Biele- It is generally assumed that nesting adult raptors feldt, unpubl. data). Adult male Broad-winged Hawks will behave normally around blinds, but one adult (B. platypterus) and Sharp-shinned Hawks (A. striatus) female Broad-winged Hawk uttered alarm calls and also have been caught at prey-transfer sites in Wisconsin attacked a cloth-covered blind, piercing it with her without causing nest desertion (E. Jacobs, pers. comm.). talons (Rosenfield 1978). In another instance an adult Raptor biologists often use blinds near the nest to female Peregrine Falcon called and attacked a blind study nesting behavior (e.g., Harris and Clement 1973, placed near her nest in West Greenland. The female Kennedy and Johnson 1986, Bielefeldt et al. 1992, and responded to an “apparent” intruding conspecific, her- see Chapter 5 of this book). Blinds are erected either self, because from the nest she could see her image during late incubation or, more often, during the early reflected in the blind’s one-way glass, which later was nestling stage during favorable weather, and often are angled to prohibit mirroring (Rosenfield et al. 1995a, R. placed 5–20 m horizontally from and a little above the Rosenfield, pers. obs). Both of these females ceased nest to facilitate observation. Some researchers also calling within 3 days of blind installation and both have placed blinds within 2 m of Eurasian Spar- fledged all their young. Adult males at these sites 356 REDUCING MANAGEMENT AND RESEARCH DISTURBANCE seemed disturbed by the blinds. One male Broad- it behavioral responses of woodland raptors, determine winged Hawk and two male Peregrine Falcons uttered their presence, or find nests (e.g., Forsman 1983, alarm calls when they flew by the blinds and appeared Rosenfield et al. 1988, Mosher et al. 1990, McLeod and hesitant at times to land on their nests (R. Rosenfield, Andersen 1998; also see Chapter 5). Prolonged playing pers. obs). There was no indication, however, that their of calls can lure some adult females repeatedly away hunting activity and prey deliveries were adversely from their nests, and broadcast calls also can attract influenced by the presence of blinds (R. Rosenfield, potential avian predators such as American Crows pers. obs). One study has reported that nestling Coop- (Corvus brachyrhynchos) (R. Rosenfield, unpubl. data). er’s Hawks exposed to frequent handling and study It is possible that broadcasts of raptor calls could result from blinds were more likely to die from human caus- in nest abandonment or depredation of eggs or es, especially shooting (Snyder and Snyder 1974). nestlings, or both. However, we are not aware of any Compared with observers hidden in blinds, the such reports, or any published recommendations by rap- recent technology of using remote cameras to record tor scientists about minimizing disturbance while using nest activities can minimize researcher disturbance at broadcast calls. On the other hand, while conducting raptor nests (Delaney et al. 1998, Booms and Fuller experiments to evaluate the probability of detecting 2003, Rogers et al. 2005). Cameras are silent, small in nesting Northern Goshawks, researchers did not use size (ca. 12 × 4 × 4 cm, L × W × H), and can be installed broadcast trials during incubation in part because they on the nest tree or a nearby tree (Delaney et al. 1998), believed that broadcasts could disturb incubating or on rock at a cliff site (e.g., Booms and Fuller 2003, females and cause egg loss (Roberson et al. 2005). Rogers et al. 2005). In time-lapse cameras, a long (75 These researchers also ended broadcast trials 2 hours m) video cable links the camera to a recording unit and before sunset to reduce the possibility of attracting noc- power source, thus allowing researchers to change tapes turnal predators (i.e., Great Horned Owls [Bubo virgini- at locations out of view of adult raptors on nests anus] and fishers [Martes pennanti]) to fledglings. (Delaney et al. 1998, Booms and Fuller 2003). Lastly, many raptor researchers investigate move- Responses of nesting birds to camera installation vary ment and other behavior of breeding adults through the by species and individuals, timing of camera placement use of radio marking and associated technology (Fuller during the nesting season, and length of time needed for et al. 1995, and see Chapter 14 of this manual). Nesting camera installation. Camera set-up time averaged 42 adults sometimes are caught and radiotagged at the incu- minutes at 20 nests of incubating Mexican Spotted bation stage. For example, across 9 years in West Green- Owls (Delaney et al. 1998), and took an average of land researchers trapped and radiotagged adult Peregrine about 2 hours at 10 nests with 4–7 day-old Northern Falcons (mostly females) at more than 600 eyries using Goshawks (Rogers et al. 2005). Camera installation noose gin traps placed among eggs. They recorded no during the mid-incubation to early nestling stage (young abandonment at any nests, and did not detect any differ- = 5 days old) took 2–4 hours at each of three Gyrfalcon ence in productivity at nests where adults were radio- cliff nests (Booms and Fuller 2003). Researchers report- tagged versus nests that were not disturbed by trapping ed no nest abandonment in response to remote cameras and radiomarking of adults (W. Mattox, unpubl. data). used with Mexican Spotted Owls (Delaney et al. 1998), Adult raptors are more commonly radiotagged dur- Cooper’s Hawks (Estes and Mannan 2003), Gyrfalcons ing the nestling stage so as not to compromise the viabil- (Booms and Fuller 2003), and Northern Goshawks ity of fragile eggs during the time it takes to capture, (Lewis et al. 2004, Rogers et al. 2005). However, Cain attach a transmitter, and allow birds to resume nesting (1985) reported abandonment of three Bald Eagle nests activities. Investigators implicitly assume that radio- after installing cameras during the late incubation and marked individuals behave and survive normally (Con- early nestling periods. In some bird studies, miniature way and Garcia 2005), especially if radio transmitters remote cameras have attracted predators. Thus, are small relative to the animal’s mass (Reynolds et al. researchers may want to camouflage or hide cameras 2004). Several studies have investigated the effects of (Green 2004). Conversely, the use of cameras may repel radio tagging on the behavior of breeding raptors, and predators and potentially bias an investigation aimed at none reported nest abandonment. However, decreased documenting nest predation (Green 2004). productivity in Golden Eagles, including nesting suc- Raptor biologists frequently use broadcasts of con- cess, fledglings per occupied territory, and brood size, in specific vocalizations during population surveys to elic- one of three breeding seasons was associated with the REDUCING MANAGEMENT AND RESEARCH DISTURBANCE 357 presence of radio transmitters (Marzluff et al. 1997). and returned to the cup (Olsen 1993). It also is possible Vekasy et al. (1996) reported no effect of radio tagging for an adult to puncture an egg or to trample small on Prairie Falcon nesting success and brood size, but young under circumstances of a sudden exit. Fortunate- indicated that biases may occur in certain years of vary- ly, these types of situations appear to be very rare. Prob- ing weather and prey availability; they suspected that lems are more likely during the days just prior to and radio-tagged female Prairie Falcons may have had lower after hatching, when adults of most species sit “tighter” productivity and thus, they tended to quickly release (some birds will stay on the nest until a climber is gravid females without attaching radio tags. In related halfway up a tree or down a cliff), making a sudden research, Spotted Owls carrying backpack transmitters departure more likely, at a time when small, and weak had lower productivity than leg-banded owls (Foster et young are dislodged easily. When researchers cannot al. 1992). Although 25 of 29 radiomarked adult Northern see clearly into a tree nest, detect other sign of young Goshawks successfully fledged young, the annual sur- (by looking for whitewash on the ground beneath a vival of breeding male goshawks that carried a tailmount nest), or otherwise determine that a nest is active, they was lower than for males that carried backpack-style often tap the nest tree in an attempt to induce detectable radio transmitters (Reynolds et al. 2004). Careful selec- movement by a tending adult to confirm occupancy. tion of an attachment method, practice on captive or wild Tapping also may cause a fast exit by an adult, who non-nesting birds and, if required, innovation and testing accidentally may dislodge ad eject eggs or nestlings can minimize potential effects of radio marking raptors from the nest. To reduce this possibility, it is better to and reduce the overall time spent attaching radios to seek a distant vantage point and use binoculars or a nesting adults (Fuller et al. 1995). spotting scope to determine occupancy. If this is not We reiterate that some species may be less tolerant possible, one should slowly approach from a distance in than others of research activity during the nesting sea- an obvious and visible manner, perhaps even making son. For instance, breeding adult Gyrfalcons are rela- sounds, so that the adults have an opportunity to detect tively shy and do not seem to habituate as readily to one’s presence and leave the nest in a less frantic man- radio tagging as do other nesting raptors. After being ner. Walking tangentially rather than directly toward a outfitted with a satellite-received, platform transmitter nest will help slow the approach and is less threatening terminal (PTT), one female Gyrfalcon in West Green- to the birds. We recommend tapping trees as a last resort land did not feed her young, which eventually died (M. and use only moderately strong repeated strikes, which Yates and T. Maechtle, pers. comm.). In another study tend to cause minimal movement in adults. When doing in Greenland using PTTs, K. Burnham (pers. comm.) so, one should watch for ejected young. In two cases a has never observed nest abandonment by Gyrfalcons, nestling was knocked completely from a nest (among but he did not radio adults until nestlings were about the thousands of visits made by the authors to nests of 20–25 days old and can thus tolerate the several hours many species of raptors across North America). In one that breeding adults, especially females, may take to of these instances, R. Rosenfield (unpubl. data) caught “accept” transmitters. a 5 day-old Cooper’s Hawk in mid-air and returned the uninjured bird to the nest where it eventually fledged. Damage to Eggs and Young by Frightened Adults Cooling, Overheating, and Loss of Moisture from Eggs or Young When incubating or brooding small young, adults often respond to human approach by hunkering down in the Eggs and small young (less than 7 days old), in particu- nest, presumably to avoid detection. Incubating or lar, are vulnerable to chilling, overheating, and dehydra- brooding adults sometimes also carefully walk to the tion when the parents are kept away from the nest. The rim of the nest before flying off. At other times, an adult temporary cooling of eggs apparently does not pose a is disturbed suddenly and bolts so quickly that the eggs serious problem during normal field procedures, and or young, which are between or underneath its feet, are some species can tolerate adult trapping procedures dur- catapulted out of the nest cup or scrape onto the nest rim ing incubation (see Nest Desertion above). Researchers or out of the nest completely. Eggs on the nest rim like- that climb raptor nests during the incubation period to ly will not be moved back into the nest by an adult, but determine clutch size generally do not report weather or sometimes young crawl back or are picked up by adults other conditions at the time they counted eggs 358 REDUCING MANAGEMENT AND RESEARCH DISTURBANCE

(Reynolds and Wight 1978, Janik and Mosher 1982, ing for intruders to leave the area. To avoid such situa- Andrusiak and Cheng 1997, Petty and Fawkes 1997). tions, keep visits as brief and unobtrusive as possible Climbs of < 10 minutes at more than 500 Cooper’s and consider weather, position of the sun, and time of Hawk nests in Wisconsin did not appear to result in nest day. If possible, do not visit nests at time of hatching, or abandonment or egg loss due to cooling (R. Rosenfield during periods of extreme weather and avoid visiting and J. Bielefeldt, unpubl. data); nests were never unshaded nests during the hottest part of the day. If vis- climbed when temperatures were < 18ºC, and the esti- its during inclement conditions are necessary and mated maximum time that females were off their nests unavoidable, put the eggs or young in a fur-lined glove during such visits for clutch counts was 20 minutes. or protective container, or cover them with a piece of Nestling raptors in hot environments, or in nests cloth or branches with leaves. Do not conduct adult exposed to direct sunlight, may face extreme thermal- trapping activities at nests until young can thermoregu- and water-balance problems. When stressed these indi- late. See Steenhof et al. (1994) and Erdman et al. (1998) viduals rely heavily on increased respiratory water loss for details. And terminate trapping activity about 2 via panting to combat hyperthermia. Heat-induced hours before sunset to allow adults ample time to return death of nestlings has been reported in several species to their nest and resume normal behavior. of raptors, including Red-tailed Hawk (Fitch et al. 1946), Galapagos Hawk (B. galapagoensis) (deVries Premature Fledging and Banding Young 1973), Golden Eagle (Beecham and Kochert 1975) and Peregrine Falcon (Nelson 1969). In most nestling birds Fledging occurs when young first leave the nest. In of prey, the only source of water (except for metabolic most species, fledging is a gradual process that includes water) is from food provided by the parents (Kirkley combinations of climbing, jumping, and flapping before and Gessaman 1990), and thus missed feedings due to flight feathers of the wings and tail are completely prolonged researcher presence may, besides diminish- grown and sustained flight is possible (Newton 1986, ing nutrient intake, compromise water balance of Rosenfield and Bielefeldt 2006). Approximate fledging chicks. Older nestlings avoid exposure to direct sunlight dates of selected North American and European raptors by moving to shaded parts of the nest, and when the nest can be found online in the Birds of North America is exposed to direct sunlight, attending adults shade accounts (Poole 2004), Newton (1979b, Table 18), and their young with outstretched wings and tail. Heat- Cramp and Simmons (1980). In most studies of raptor stressed nestlings tend to position themselves on the productivity researchers visit nests to count and, at the perimeter of the nest, presumably to enhance the effec- same time, band young. Fyfe and Olendorff (1976) sug- tiveness of convective cooling (Kirkley and Gessaman gested that the optimum time for banding is when the 1990). Some young may be heat-stressed and already young are approximately one-half to two-thirds fledg- near their limits of tolerance even without the added ing age. This is because until about one-half of fledging burden of disturbance. The situations vary with location age, a nestling’s legs and feet are not fully grown, and a (e.g., cooling is more likely in the Arctic whereas dry- band may slip down a leg and encircle the foot. Prior to ing occurs in desert or grassland areas, and overheating two-thirds fledging age, nestlings tend to move mini- in lower latitudes), although panting in response to mally when researchers are at the nest. Nestlings also direct sunlight can occur even at seemingly cool tem- tend to struggle less when handled at these ages, and peratures. For instance, a pair of 17 day-old Red-tailed banding at this stage is relatively straightforward and Hawks began to pant in the early-morning sunlight at proceeds relatively quickly. Thus, overall time at the 08:30 when the air temperature was 13ºC (Kirkley and nest is reduced. When a researcher reaches a nest with Gessaman 1990). Temperature and humidity are gener- older, unfledged youth, the young often spread their ally most favorable for nestlings in forested areas. wings, move quickly to the opposite edge of the nest, Extremes are possible in all places however, and should and lean backward (often precariously) in a defensive always be considered. Wind, precipitation, and direct posture. At this age, young are easily startled and may sunlight can exacerbate the situation. The times that fledge or leave the nest prematurely by trying to fly off, nestlings can be exposed to adverse conditions are or by stepping to the edge of the nest or onto branches increased in timid species such as Gyrfalcons, Golden or cliff ledges from which they may fall. The results of Eagles, and Snowy Owls (B. scandiaca), where parental such falls depend on the bird’s age and condition, and birds stay away from the nest for extended times wait- where it lands. Finally, there always is the risk of injury, REDUCING MANAGEMENT AND RESEARCH DISTURBANCE 359 loss, or increased vulnerability to predation due to pre- (Bechard and Schmutz 1995). A universal application of mature fledging. an 80% fledging-age metric may make it difficult for When reaching for older nestlings we recommend researchers to capture mobile young, lead to unsafe moving a hand slowly toward and at the level of the indi- handling of older young, and result in premature fledg- vidual’s feet, and allowing the bird to grab your hand if ing, all of which can result in inaccurate productivity possible so as to establish reliable contact. If several estimates. Consequently, we recommend that counts birds are about to jump from a tree nest, try and capture and banding of young should be done when young are them one at a time by reaching up and letting them grab at about 70% fledging age for Cooper’s Hawks in a hand without putting your (obtrusive) head and shoul- British Columbia, North Dakota, and Wisconsin ders above the nest. A makeshift poultry hook is useful (Rosenfield and Bielefeldt 1999, 2006; Stout et al. in some situations (Grier 1969). We also recommend 2007; A Stewart, unpubl. data); and at about 65% fledg- putting older young in a backpack to confine their move- ing age for Red-shouldered Hawks (B. lineatus) in Wis- ments. When the pack is closed, the darkness inside the consin (E. and J. Jacobs, unpubl. data); and 55% fledg- bag seems to calm the nestlings. If young do jump, take ing age for Sharp-shinned Hawks in Wisconsin (E. care to mark where they went, retrieve them and, if there Jacobs and R. Rosenfield, unpubl. data). Researchers are no injuries, place in the nest one at a time. Again should be cognizant of the possibility of population- keep most of your body below the nest and replace the specificity in nestling development when timing their “jumper” nestlings in the reverse order in which they nest visits, and should first learn how to handle nestling jumped. Thus, the young that jumped first and, presum- raptors in the field by spending time in the field with ably, would be more likely to jump again, will be mini- experienced researchers. mally disturbed. One should then depart slowly and qui- etly from the nest. Premature fledging is best avoided by Avian and Mammalian Predation visiting nests early in the season. When older nestlings are encountered, they are best left alone or approached Fyfe and Olendorff (1976) indicated that avian preda- slowly and handled with extra caution. If handled care- tors including jaegers, gulls, and corvids often visually fully and slowly, young can be distracted from fledging cue onto unattended nests, and that after researchers had and will adjust to the presence of the intruder. We also disturbed nests, predators might raid nests while the recommend that observations from blinds be discontin- adults are away. Although in non-raptorial species avian ued about 3 to 4 days before the young are due to fledge predators have been shown to respond to or follow field to avoid causing them to leave the nest prematurely workers and to prey on nests visited by investigators (Geer and Perrins 1981, Rosenfield et al. 1995). there is no direct evidence of this in the literature con- Steenhof (1987) recommended visiting nests when cerning raptor nests (Gotmark 1992). Even so, a crow young are about at 80% fledging age to assess nest suc- (Corvus sp.) has been observed throwing one of two, cess and productivity, a somewhat later nest visitation unattended, small Great Horned Owl nestlings out of a time than the one-half to two-thirds fledging age dis- nest about 30 minutes after a researcher climbed to it. cussed above (Fyfe and Olendorff 1976). Steenhof and Although the researcher returned this unhurt bird to its Newton (Chapter 11, this volume) now encourage nest, several days later researchers found both owlets determining an appropriate standard for timing of nest dead at the base of the nest tree and attributed their visits to assess productivity and band young of various deaths to attacks by crows due to his presence at the raptor species. There are, however, temporal differences nest (Craighead and Craighead 1956). Adult Cooper’s in behavioral development among species, and among Hawks are frequently mobbed and rarely struck by populations of the same species (i.e., young may devel- Northwestern Crows (C. caurinus) when researchers op more slowly or more quickly in some populations are near their nests in British Columbia, but the crows [Rosenfield and Bielefeldt 1993a, 2006; Curtis and do not visit nests during the presence of researchers and Rosenfield 2006; S. Postupalsky, pers. comm.). Tempo- there is no evidence of unattended eggs or nestlings ral differences are sometimes accentuated in raptors being preyed upon by crows after visits (A. Stewart and because of reversed size dimorphism, in which smaller R. Rosenfield, pers. obs.). Gotmark (1992) suggested males develop faster and fledge earlier than females. that when avian predation has been documented, the For example, male Ferruginous Hawk nestlings leave predators responded opportunistically to unattended nests about 10 days earlier than female nestlings nests or young rather than to observer presence per se. 360 REDUCING MANAGEMENT AND RESEARCH DISTURBANCE

Some authors assume or emphasize that mam- 1994, Erdman et al. 1998). We recommend using broad- malian predators might find nests by following scent casts of conspecific calls while conducting adult trap- trails left by researchers during their nest visits (e.g., ping activities at nests — especially in wooded areas Hamerstrom 1970, Poole 1981, Gawlick et al. 1988), where visibility is limited — because they often more and that this problem is particularly serious for ground- quickly draw attention of parents to a decoy and can nesting raptors (Fyfe and Olendorff 1976). Mammals reduce time spent at the nest (Erdman et al. 1998, R. also are sometimes thought to follow tracks in the veg- Rosenfield, unpubl. data). Steenhof et al. (1994) report- etation made by observers. In his review, Gotmark ed that broadcasting Great Horned Owl calls did not (1992) found no evidence of increased predation by expedite trapping American Kestrels. mammals due to researcher presence at nests. He also Many species of nesting raptors are surveyed or was unable to locate a study that documented mam- studied from fixed-wing aircraft or helicopters without malian predators following observers. He noted, how- adverse disturbance effects (e.g., Grier et al. 1981, ever, that if precautions like avoiding the creation of Kochert 1986, Andersen et al. 1989, Watson 1993, trails in vegetation is effective (as recommended by McLeod and Andersen 1998, Kochert et al. 2002). Hamerstrom [1970]) and were being taken by Knowledge of a species’ tolerance to low-level flying researchers, such behavior may have influenced his aircraft is critical and researchers should use only expe- inability to find investigator effects. Finally, to avoid rienced pilots when surveying raptors (Kochert 1986). drawing attention to a nesting area, one should with- In a novel study, White and Nelson (1991) monitored draw from the site to complete field notes. habitat use and the hunting behavior of a male Peregrine Falcon and a female Gyrfalcon by following these nesting adults (even in hunting stoops!), with helicopters at Mishandling Birds a distance of 30–50 m. They emphasized that despite Both raptors and handlers can be injured during improp- the potential lethal threat of doing so, both to the birds er handling. Young birds with growing bones, feathers, and the human observers (some Gyrfalcons attack heli- and talons are particularly vulnerable (see Chapter 12). copters), the technique produced information almost How to handle birds correctly is best learned in the field impossible to collect by more conventional methods from someone with experience. (see Chapter 5). The young at one of their study nests, however, were depredated about 3 weeks after the pro- ject ended. But either the same adult pair or another Miscellaneous Considerations used the same eyrie the following year. A number of precautions can help reduce disturbance to raptors by observers, researchers and managers. These include using teams of two people instead of single ACKNOWLEDGMENTS individuals and giving special care to banding and marking of raptors. Using two workers enhances safety Our research has been funded by the National Audubon both for the researchers and birds, and permits greater Society, the National Wildlife Federation, the Canadian efficiency in note-taking and carrying equipment, Wildlife Service, the U.S. Fish and Wildlife Service, the which, in turn, reduces the amount of time spent in the U.S. Forest Service, the North Dakota Game and Fish area. In addition, Speiser and Bosakowski (1991) noted Department, the North Dakota, Wisconsin, and Great that two or more observers elicited milder, less aggres- Lakes Falconers’ Association, the Personnel Develop- sive encounters with nesting adult goshawks (which ment Committee and the Letters and Science Founda- sometimes strike researchers). tion of the University of Wisconsin-Stevens Point. We When trapping breeding adult raptors, some thank K. Burnham, W. Stout, W. Mattox, P. Kennedy, S. researchers advocate using mist nets rather than dho- Postupalsky, E. Jacobs, and A. Stewart for providing gazas (see Chapter 12). The use of mist nets probably information and helpful discussions regarding lowers time spent at the nest because they do not col- researcher disturbance. D. Ellis, J. Bielefeldt, K. Steen- lapse after a strike and, therefore less time is needed to hof, A. Stewart, and K. Bildstein improved the manu- reset the net. Contact between a lure owl and a trapped script with their editorial suggestions. R. Rosenfield bird rarely occurs with mist nets, a possibility that often acknowledges sabbatical support of his campus. is uncontrollable with the dho-gaza (Steenhof et al. REDUCING MANAGEMENT AND RESEARCH DISTURBANCE 361

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